The statements come amid the reported presence of two Chinese military planes on Panganiban or Mischief Reef, and China's unveiling of a monument to mark its construction work in Kagitingan or Fiery Cross Reef.

Both are in the contested Spratly Islands in the South China Sea, which is being claimed by the Philippines, China, Vietnam, Taiwan, Malaysia, and Brunei.

Esperon said these may be interpreted as "increased military activity," but added these were intended for training only.

The Department of Foreign Affairs has repeatedly said it will take diplomatic action whenever necessary, including the filing of a diplomatic protest against China.

China has refused to acknowledge the July 2016 arbitral ruling that awarded to the Philippines areas in the South China Sea that lie within the country's 200-mile exclusive economic zone. The Philippines calls this the West Philippine Sea. China continues to claim the South China Sea in its entirety.

Duterte has repeatedly said the country cannot afford to go to war against China, but has promised to bring up the arbitral ruling with the East Asian giant during his term.